The present invention provides a new catalytic procedure for preparing azines from ketones or aldehydes in the presence of ammonia and hydrogen peroxide.
It is known that aldehydes react with ammonia in a complex manner to form various products of addition, condensation or polymerization. (See S. Patai, The Chemistry of the Carbon-Nitrogen Bond, Interscience, London 1970 page 67). It is known also that aldehydes are capable of reacting with hydrogen peroxide to form unstable peroxide products and that aldehydes can react together with both hydrogen peroxide and ammonia to give rise to peroxide products. (See J. Chem Soc. 1969, C, page 2678).
It is likewise known that ammonia, hydrogen peroxide and a ketone can react together to produce aminoperoxides. (See, for example, J. Chem. Soc., 1969, C, page 2663) and that these reactants in the presence of tungstic acid or molybdic acid catalyst, can produce an oxime. (See, for example, J. Gen. Chem. (U.S.S.R.) 1960, 30, page 1635).
It is known, furthermore, that primary and secondary amines are easily oxidized by various compounds into oxygenated products such as hydroxylamines, nitro or nitroso derivatives, oximes, azoxy compounds, amides and other related compounds depending on the particular structure of the reactants and the reaction conditions. For example, the oxidation of primary aliphatic amines into nitroalkanes by means of peracetic acid has been described in J. Am. chem. Soc. 79 5528 (1957). Similar reactions using other percarboxylic acids are described in The Chemistry of the Nitro and Nitroso Groups Part I, edited by H. Feuer, page 309 (Interscience, N.Y., 1969).
The primary aromatic amines have been oxidized into nitroso, nitro or corresponding azoxy derivatives by pure percarboxylic acids or by a mixture of acetic acid and hydrogen peroxide in 30% aqueous solution (J. Am. Chem. Soc. 82 3454 (1960)).
Aniline also has been oxidized to azoxybenzene by hydrogen peroxide in the presence of acetonitrile. (J. Org. Chem. 26 659 (1961)).
Now, earlier applications for patent, commonly assigned with the instant application, have described several new procedures for synthesizing azines (I) by oxidizing ammonia in the presence of a ketone or aldehyde carbonyl compound (IV) with various peroxide reagents according to the general scheme: ##STR1## wherein R.sub.1 and R.sub.2 are alkyl or aryl groups.
In addition to the patent disclosures enumerated below, see also Tellier, Mathais, Schirmann and Weiss, Bull. Soc. Chim. Fr. 1972 (7) 2954; Schirmann and Weiss, Tetrahedron Letters, No. 7 635-636 (1972); Mathais, Schirmann, Tellier and Weiss, Tetrahedron Letters, No. 6, 529-530 (1972).
The oxidation reaction of Equation 1 can be accomplished with monopersulfuric acid (French application for patent Ser. No. 73/05.504 of Feb. 16, 1973), with a percarboxylic acid (pending U.S. application Ser. No. 290,507 filed Sept. 20, 1972, now French Pat. No. 2,155,134), or with a diacyl peroxide (U.S. Ser. No. 308,836 filed Nov. 22, 1972, corresponding to French applications Ser. Nos. 71/41867 and 72/08580, the former having matured into French Pat. No. 2,161,349, the latter being an application for Certificate of Addition thereto).
In strong contrast to the above-mentioned peroxide reagents, hydrogen peroxide by itself is not satisfactory. When it is attempted to oxidize ammonia and an aldehyde or ketone by simple reaction with hydrogen peroxide, many competing reactions take place simultaneously with little or no yield of azine. However, members of the present inventive entity have unexpectedly found that hydrogen peroxide can be used effectively to form azines selectively when certain adjuvant substances are also present, acting catalytically or as coreactants in a manner as yet not completely understood.
Thus, good yields of azines are obtained if the mixture of aldehyde or ketone with H.sub.2 O.sub.2 and ammonia contains also a nitrile as coreactant (U.S. application for Pat. Ser. No. 152,413 filed June 11, 1971, corresponding to French applications for patent and certificate of addition respectively Ser. No. 70/46,994 filed Dec. 29, 1970 and Ser. No. 71/06,215 filed Feb. 24, 1971 which have since matured respectively into French Pat. Nos. 2,092,734 and 2,127,288).
Good yields of azines are also formed when the hydrogen peroxide, carbonyl compound and ammonia are reacted in the presence of coreacting amides or imides of carboxylic acids whose ionization constant is greater than 5 .times. 10.sup.-.sup.5 (U.S. Ser. No. 341,057 filed Mar. 14, 1972, corresponding to French Pat. No. 2,177,215) or in the presence of cyanide compounds as co-reactants (French Pat. No. 2,176,244), in the presence of certain salts as catalyst (U.S. Ser. No. 267,921 filed June 30, 1972) or in the presence of certain esters as coreactants (U.S. Ser. No. 340,762 filed Mar. 13, 1973), or with a derivative of selenium as catalyst (Application for French patent Ser. No. 73/04,633 filed Feb. 9, 1973).
It has also been ascertained that when a system of hydrogen peroxide, ammonia, carbonyl compound (aldehyde or ketone) and one of the special adjuvants recited above contains also a primary and/or secondary amine (III), there takes place in addition to the reaction summarized in equation (1) above, the formation of a hydrazone (II) according to the following equation (2): ##STR2## wherein the R groups can be such as those described further below herein in respect to the instant invention. See, for example, Application for U.S. patent Ser. No. 406467 filed Oct. 15, 1973, corresponding to application for French patent Ser. No. 72/36,505 filed Oct. 16, 1972; also the aforementioned French application Ser. No. 73/04,633 filed Feb. 9, 1973.
It is to be emphasized that when amides are used as coreactants according to the aforementioned applications Ser. No. 341,057 or 406,467, a limitation required in order to get good yields of azines or hydrazones respectively is that the carboxylic acid from which the amide is derived must be sufficiently strong to have a dissociation constant at least equal to about 5 .times. 10.sup.-.sup.5, i.e. its pK must be less than about 4.3.